This is NOT,.. a personal issue, But a target for me,...If you dont filter it cumming in why filter it going out??? It wood be like filtering the exaust on a truck engine and not the air going threw the intake, Eric
uummmm...NO
Just what is the byproduct or contaminant that is being produced by squeezing oil?
There is none unless operator error occurred, like leaving your funnel under your metal lathe and not cleaning it, then using it to fill your hydraulic tank. Or maybe applying pipe thread sealant over-liberally on female and male threads. Or leaving a fill or vent cap off while running the splitter because your too lazy to remember where you left it last time you checked the fluid level. Or maybe you drilled and threaded the tank for a temp/fluid level gauge and didn't properly clean it.
Get the idea? Squeezing oil through some hoses and such
doesn't inherently add contamination. The only thing that would go through the pump came from the pump itself. Ultra-miniscule particles of metal that flake off over years and decades, that eventually make a pump less efficient, well, guess what? They "went through the pump". The only other moving part that could cause "contamination" is the o-rings as they slide across the ram's shaft. Those would be filtered before going through the pump.
As KsWoodsMan says, "If it starts clean, it stays clean", unless you don't have the wherewithall to keep it clean. Such as running a truck without an air filter. Nothing can save people from themselves. Just as you can't save their equipment from them.